Today, many medical conditions are treated by placing medical devices or appliances within a patient. Many medical conditions necessitate the use of these medical devices for supporting of blood vessels or other lumens within the body that have been re-enlarged following, for example, cardio balloon angioplasty.
With regard to angioplasty, typically an endovascular implant known as a stent is placed within the blood vessel. A stent is usually tubular in shape and may have a lattice or connected-wire tubular construction. The stent is usually placed within the vessel in a compressed state and then allowed to expand. Self-expanding and balloon-expandable stents are well known. The support provided by a stent prevents the vessel from either closing, referred to as restonosis, or suffering spasms shortly after the angioplasty procedure.
In addition to the structural support provided by a stent, it is known to provide coatings containing medicines upon an outer surface of the stent. Here, the outer surface is meant to indicate that surface that is in direct contact with the vessel wall. The coating on the outer surface of the stent is absorbed by the vessel wall, and the medicine in the coating is absorbed.
There are many proposed methods and systems for providing this medicinal coating to the stent. The methods are known to include dipping, contact coating, spraying and electrostatic deposition.
The precise control of the coating process is important for a number of reasons including, but not limited to, the cost of the medicine in the coating, the mechanics of the stent itself in that the coating should not interfere with proper operation of the stent and the requirements, at least in the United States, of an FDA regulated device.